Process for preparing indoxyls and indigo coloring-matters.



No Drawing.

must be considered practlcable one whlc UNITED s'TATEsrntr NT OFFICE,

ARNOLD BAHTJEN, or

HAMBURG, (383E131);ANY:v

PROCESS FOR PREPARING INDOXYLS AND INDIGO COLORING-MATTERS.

To all whom it may concern:

Be it known that I, ARNOLD RAHTJEN, asubject of the German Emperor, andresi dent of Hamburg, Germany, have invented certain new and usefulImprovements in Processes of Preparing Indoxyls and IndigoColoring-Matters, of which the following is a specification.- I

7 It is a well known fact that substances which contain the group NHCHCO one or more times in the molecule may be converted by melting withalkali hydroxids into indoxyls from which indigo may be prepared inthewell known manner. However, the yields obtained by this process, as, forinstance, whenv phenylglycinv (anilidoaceticaeid) is' used, are so smallthat the process s a commercially imcannot be employed for themanufacture of indigo on a large scale. It has been new found that anexcellent yield of indoxyls and, consequently, of indigo maybe obtainedby electrolyzing of a diaphragm;

substances of the aromatic or cyclic type and containing an aryl grouplinked to one on more groups of thegeneral type (NRCH CO), in which Itrepresents hydrogen or an organic radical, in admixture with bodiescapable of yielding metal ions upon electrolysis, such as the alkalihydrates, singly or admixed, oxids or hydrates of alkaline earths, orelectrolyzable salts of alkalis or alkaline earths capable of yieldingmetal ions. Substances which serve as fluxes or diluting a ents maybeen'lployed, advantageously. El ectrolysis' may be carried out with orwithout the employment The experiments made to date have given yields upto and beyond 7 0% (seventy per cent.) of the theory.

In general it may be stated that substances of the aryl-glyciu type aresuitable for employment in this process, including under this genericterm the aryl-glycins pe-r -se and their homologues, esters and salts,as well as their acet-yl and othef'derivat-ives. When phenylglycin (C HNHCH COOH) is em Specification of Letters Patent. Patented Feb, 14.1911, Application filed November 2, 1910. Serial No. 590,340.

ployed, the reaction which occurs is sometimes written as follows:

fsc

water being eliminated from the phenylglycin with formation of indoxyl.Equations such as this must be taken, however, as purely theoretical andas merely indicative of probable reactions, rather than as representingascertained facts. This result could not have been anticipated, for itmight have been expected that theorganic bodies employed,"such as saltsof phenylglycin, etc., would be entirely decomposed by the electriccurrent. Such is not the case, but with sensitive substances it is oftenuseful to employ a diaphragm whereby the hydroxyl ions, "which areprejudicial, may be. conveyed in the simplest possible manner into pheanode chamber and thus rendered harmess. v

The favorable result of employing the electric current appears to residein the fact that the alkaline meta-l is'enabled to react in stat-umzsccndi and in a state of fine divi sion that cannot be obtained bymechanicalmeans.

The ten'iperature of the materials, and

the tension and the density ofthe current employed may vary betweenlarge limits.

Good outputs are obtained when the electrolysis'is carried on at atemperature between 160-300 degrees C. and with -1 to 10 volts and 0.2to 20,;a mpe'res per square decimeter of surface of -.electrodes.

Typical substances which may be employed are, phenylglycin-phenylglycinand phenylhydantoin as well as their homologues, salts, ethers, etc.,and their acetyl and other derivatives.) The electrodes and diaphragmsemplo 'ed maybe those usually utilized for electro yzing alkalihydroxids,

-alkali hydroxids' alone.

free in molecular form, into the period of formation type and treatingIn a typical example of my invention, 100 parts of a molecular mixtureof sodium and potassium hydroxids are mixed with 30 parts ofacetylphenylglycin-o-carbonate of potassium and the mixture heated toabout 220 to 260 degrees C. and fused in the cathode chamber of asuitable electrolytic cell. The anode Chamber may be charged withthe-same molecular mixture of the The mixture in each chamber maycontain alkaline earths or salts and alkalis or alkaline earths ordiluting fluxes. The cell may serve as a cathode and carbon be employedas an anode. The electrolysis may be advantageously carried out wit-h acurrent of about 4 to 6 volts and about 2 to 5 amperes per squaredecimeter, the liquid mass being well stirred. The operation iscontinued until for each molecule of substance a little more than oneatom of alkali metal has been set free, which may easily be calculatedwith the aid of the givendata. After cooling down the molten mass, itmay be introduced into water and the indigocoloring matters prepared inthe well known manner. mode of operating, as that have been made, of thetheory.

Suitable precautions may be taken during the electrolysis to obviate orremove byproducts of the reaction, such as free alkali metal and water.

During the electrolysis, suitable reactive gases or vapors such asammonia or hydrazin may be conveyed through or over the mass in order toconvert liberated sodium etc., set

corresponding metal amids or metal imids. The re action may be carriedout under reduced pressure or vacuum and I preferably carry out theelectrolysis in a vigorous or lively manner at the beginning, and duringthe of water so that the water formed is at once rendered harmless.

Having now fully described my said invention, what I claim and desire tosecure by Letters Patent, is-

'1. A process of preparing indoxyls and indigo coloring bodies whichcomprises electrolyzing a mass comprising alkali hydrox ids and asubstance ot the aryl-glycin type, and treating the resulting massto'recover indoxyl and indigo theretrom.

2. A. process of preparing 'indoxyls and indigo coloring bodies whichcomprises electrolyzing a mass comprising alkali hydroxids and otherelectrolyzable inorganic substances andra, substance of the aryl-glycinHie resulting mass obtained to recover indoxyl and indigo therefrom.

3.A process of preparing indoxy'ls and The output with this shown byexperiments is about 70 per cent.

indigo coloring bodies which comprises electrolyzing a mass comprisingalkali hydroxids and diluting agents and a substance of the aryl-glycintype and treating the resulting mass obtained to recover indoxyl andindigo therefrom.

at. A. process of preparing indoxyls and indigo coloring bodies\vhichcomprises elec trolyzin a mass comprising alkali hydroxids mixedwith fluxes and a substance of the aryl glycin type and treating theresulting mass to recover indoxyl and indigo therefrom.

A process of preparing indoxyls and indigo coloring bodies whichcomprises elec' Irolyzin a mass comprising alkali hydroxids andotherelectrolyzable inorganic substances and diluting agents and asubstance of the aryl-glycin type and treating the resulting massobtained to recover indoxyl and indigo therefrom.

6. A process of preparing indoxyls and indigo coloring bodies whichcomprises electrolyzing a mass comprising alkali hydroxids and otherelectrolyzable inorganic substances and fluxes and a substance of thearyl-glycin type and treating the resulting mass obtained to recoverindoXyl and indigo tl'ierefron'i.

7. A process of indigo coloring trolyzing a mass comprising an alkalihydroxid and a substance of the -aryl-glycin type and during suchelectrolysis removing by-products of the reaction, and treating theresulting mass obtained to'recover indoxyl and indigo therefrom.

8. A process of indigo coloring bodies Which comprises elecpreparingindoxyls and trolyzing a'mass comprising an alkali hy-- droXid and othersubstances capable of evolving metal ions, a fiuxing body, a dilutbodyand a substance of the aryl-glycin type, and treating the resulting massobpreparing indoxyls and bodles which comprises elec- I Jjb taincd torecover indpxyl and indigo therefrom;

9. A process of preparing indoxyls and indigo coloring bodies whichcomprises electrolyzing a mass comprising alkali hydroxids and asubstance of the aryl-glycin type and during such electrolysiscontacting areactive gas with such mass to prevent formation of freemetal, and treating the resulating mass obtained to recover indoxyl andindigo therefrom.

10. A process of preparing indoxyl' and indigo coloring bodies whichcomprises eleclrolyzing a mass comprising alkali hydroxids and asubstance of the aryl-glycin type, the electrolysis being carried onwith an increased current during the formation of water so that thewater formed is at once rendered harmless, and treating the result- Iing mass obtained to. recover indoxyl and indigo therefrmn.

It. A process of preparing indoxyls and indigo coloring bodies, whichcomprises electrolyzing a mass comprising alkali hydroxids and asubstance in which an aryl. group is. linked to the group NROH2(JO andtreating the resulting mass to produce indigo coloring bodies.

12. A process of preparing indoxyls and indigo coloring; bodies, whichcomprises electrolyzing a mass comprising alkali hydroxids and asubstance in which-a phenyl 'roup is linked to the group -NR-CH 10-, andtreating the resulting mass to produce L5 indigo coloring bodies.

In testimony whereof I have hereunto set my hand in presence of twoWitnesses.

' ARNOLD RAHTJEN. Witnesses:

ERNEST H. L. MUMMEN Horr, IDA. CHRIST. HAFERMAN'N.

